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Spatial Distribution of Anopheles gambiae and Anopheles funestus and Malaria Transmission in Suba District, Western Kenya

Published online by Cambridge University Press:  19 September 2011

Josephat I. Shililu ,
Charles M. Mbogo ,
Clifford M. Mutero ,
James T. Gunter ,
Chris Swalm ,
James L. Regens ,
Joseph Keating ,
Guiyun Yan ,
John I. Githure  and
John C. Beier
Josephat I. Shililu
Affiliation:
Hurnan Health Division, International Centre of Insect Physiology and Ecology (ICIPE), P. O. Box 30772–00100 Nairobi, Kenya Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya
Charles M. Mbogo
Affiliation:
Centre for Geographic Medicine Research-Coast, Kenya Medical Research Institute (KEMRI), P. O. Box 428, Kilifi, Kenya
Clifford M. Mutero
Affiliation:
Hurnan Health Division, International Centre of Insect Physiology and Ecology (ICIPE), P. O. Box 30772–00100 Nairobi, Kenya CGIAR System-wide Initiative on Malaria and Agriculture (SIMA), International Water Management Institute (IMWI), 141 Creswell Street, Silverton 0184, Private Bag X 813, 0127 Silverton, Pretoria, South Africa
James T. Gunter
Affiliation:
Institute for Science and Public Policy, Sarkeys Energy Center, University of Oklahoma, 100 E. Boyd Room 510, Norman, OK 73019–1006, USA
Chris Swalm
Affiliation:
Department of Pharmacology, Tulane University Health Science Center SL18, 1430 Tulane Av, New Orleans, LA 70112–2699, USA
James L. Regens
Affiliation:
Institute for Science and Public Policy, Sarkeys Energy Center, University of Oklahoma, 100 E. Boyd Room 510, Norman, OK 73019–1006, USA
Joseph Keating
Affiliation:
Deparrment of International Health and Development, TB46, School of Public Health and Tropical Medicine, Tulane University, 1440 Canal St., New Orleans, LA 70112, USA
Guiyun Yan
Affiliation:
Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY 14260, USA
John I. Githure
Affiliation:
Hurnan Health Division, International Centre of Insect Physiology and Ecology (ICIPE), P. O. Box 30772–00100 Nairobi, Kenya
John C. Beier
Affiliation:
Department of Tropical Medicine, School of Public Health and Tropical Medicine, SL 17, Tulane University 1430 Tulane Ave., New Orleans, LA 70112, USA
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Abstract

The study reported here evaluated the distribution, relative abundance, and malaria transmission potential of Anopheles mosquitoes at 30 sites representing different ecological strata in western Kenya. Seasonal variation in anopheline densities and transmission potential, as expressed by Entomological inoculation rates (EIR), was investigated. Of the 6491 indoor resting anopheline mosquitoes collected at the 30 sites, 91.3 % (n = 5926) were An. gambiae s.l. and 8.7 % (n = 565) were An. funestus with an average house density of 6.58 and 0.63, respectively. Analysis of the data indicated significant variation in mosquito densities between study sites, species and season. High densities of both An. gambiae and An. funestus were recorded in the northern and northeastern parts of the district, while generally low densities were recorded in the south. Anopheles gambiae s.s. and An. arabiensis comprised 60.3 % (n = 3573) and 39.7 % (n = 2352) of the total number of An. gambiae s.l. mosquitoes collected, respectively. The composition of the An. gambiae s.l. sibling species showed temporal and spatial variation. Entomologic inoculation rates were estimated at 1.55 and 0.12 infective bites per person per month for An. gambiae s.l. and An. funestus, respectively. This study reveals considerable seasonal and site-specific variation in vector distribution, composition and transmission potential. Application of control interventions must therefore consider seasonal variations since the vectorial system changes quite rapidly over a short period of time.

L'étude présentée ici évalue la distribution, l'abondance relative, et le potentiel de transmission du paludisme par des moustiques anophèles dans 30 localités représentatives des différentes conditions écologiques de l'Ouest du Kenya. La variation saisonnière des densités d'anophèles et du potentiel de transmission, exprimées par les taux d'inoculations Entomologiques (EIR), est examinée. Sur les 6491 anophèles récoltées au repos à l'intérieur des maisons dans les 30 localités, 91,3% (n=5926) sont des An. gambiae s.l. et 8,7% sont des An. funeslus avec une densité moyenne par maison de 6,58 et 0,63 respectivement. L'analyse des données indique une variation significative des densités de moustiques entre les sites étudiés, l'espèce et la saison. Des densités élevées à la fois d'An, gambiae s.l. et An. funestus ont été observées dans le nord et le nord est du district, alors que des densités généralement faibles ont été observées dans le sud. An. gambiae s.S. et An. arabiensis représentent respectivement 60,3% (n=3573) et 39,7% (n=2352) du nombre total de An. gambiae s.l récolté. La composition des 2 espèces d'An, gambiae s.l. montre une variation temporelle et spatiale. Les taux d'inoculations entomologiques sont estimés respectivement à 1,55 et 0,12 piqûres infestantes par personne et par mois pour'An. gambiae s.l. et An. funestus. Cette étude révèle une variation considérable de la distribution, de la composition et du potentiel de transmission des vecteurs selon la saison et la localité. La réalisation de campagnes de lutte doit par conséquent prendre en compte les variations saisonnières puisque le complexe vectoriel change très rapidement en un temps très court.

Keywords

Anopheles gambaieAnopheles funestusspatial distributionEIRvector controlAnopheles gambaieAnopheles funestusdistribution spatialeEIRcontrôle vectoriel
Type
Research Articles
Information
International Journal of Tropical Insect Science , Volume 23 , Issue 3 , September 2003 , pp. 187 - 196
Copyright
Copyright © ICIPE 2003

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